1. Field of the invention
The present invention relates to a vehicular alternator and a method of producing the vehicular alternator, in particular, relates to a vehicular alternator having a magnet protection mechanism capable of protecting permanent magnets disposed between claw poles, and a method of producing the vehicular alternator
2. Description of the Related Art
As rotor of a vehicular alternator, there is a Lundell type rotor mechanism composed of odd-number claw poles and even number claw poles. Each of odd number claw poles is supported at one end part in an axial direction of the rotor and extending toward the axial direction. Each of an even number of claw poles is supported at another part and extends toward the axial direction. In the Lundell type rotor, the odd-number claw poles and the even number claw poles are alternately arranged in the circumferential direction of the rotor. Because the claw poles adjacent to each other in the circumferential direction are magnetized in opposite directions, a leakage magnetic flux between both the adjacent claw poles reduces the output of the vehicular alternator. In order to avoid the leakage magnetic flux generated between the claw poles, various types of a vehicular alternator using magnets are widely used. In such a vehicular alternator using magnets, a permanent magnet is placed between the claw poles adjacent to each other in the circumferential direction of the rotor.
However, centrifugal force of a large magnitude is generally applied to a flange of those permanent magnets during the rotation of the rotor. Because vibration force generated by applied force in the circumferential direction during/acceleration of the rotation of the rotor, by a strong magnetic field and by external vibration further applied to the permanent magnets, it is necessary to have a mechanism capable of efficiently fixing each permanent magnet to the corresponding claw poles in the rotor in order to avoid any displacement of each permanent magnet in the claw poles of the rotor. Permanent magnets are generally breakable and there is a demand of how to easily handle permanent magnets into the rotor during the assembling. In the techniques according to the related art, each permanent magnet is covered with a magnet holder made of non-magnetic material and each permanent magnet is adhered onto an inner surface of the magnet holder. In other words, fixing the permanent magnet to the claw pole actually means fixing each magnet holder to the corresponding claw pole.
Two related art documents, Japanese patent laid open publication No. JP H10-201150 and Japanese patent laid open publication No. JP-2006-109573, whose applicant is the same as the applicant of the present U.S. patent application according to the present invention, have disclosed a connection-type magnet holder mechanism for a rotor, where each magnet holder is connected by a plate shaped connecting member. The adaptation of such a plate-shaped connecting member to the magnet holders can effectively enhance the anti-vibration function for the permanent magnets in the rotor. Japanese patent laid open publication No. JP H10-201150 has further disclosed an elastic buffer mechanism in which a part of the magnet holder accommodating a permanent magnet faced to a claw pole is cut or bent. Japanese patent laid open publication No. JP 2006-109573 has further disclosed a mechanism in which thermosetting resin is impregnated into a gap between the magnet holder and the permanent magnet.
However, the connection-type magnet holder mechanism disclosed in JP H10-201150 requires a complicated manufacturing step because each holder of a rectangle prism shape or a box shape made of resin must be fixed to a connection part of a ring shape and the accuracy of an arrangement-position of the permanent magnet is decreased by a position error between the magnet holder and the connection part. In the related art technique JP H10-201150, the reliability of the strength of the connection is lost between the connection part and the magnet holder for accommodating the permanent magnet.